#include <fcntl.h>
#include <sys/mman.h>

#include "apue.h"

#define COPYINCR (1024 * 1024 * 1024)  //表示1GB容量
int main(int argc, char **argv) {
  int fdin, fdout;
  void *src, *dst;
  size_t copysz;
  struct stat sbuf;
  off_t fsz = 0;

  if (argc != 3) err_quit("usage: %s<fromfile><tofile>", argv[0]);
  if ((fdin = open(argv[1], O_RDONLY)) < 0)
    err_sys("can't open %s for reading ", argv[1]);
  if ((fdout = open(argv[2], O_RDWR | O_CREAT | O_TRUNC, FILE_MODE)) < 0)
    err_sys("can't creat file of %s for writing ", argv[2]);

  if (fstat(fdin, &sbuf) < 0) err_sys("fstat error");
  if (ftruncate(fdout, sbuf.st_size) < 0) err_sys("ftruncate error");

  while (fsz < sbuf.st_size) {
    if ((sbuf.st_size - fsz) > COPYINCR)
      copysz = COPYINCR;
    else
      copysz = sbuf.st_size - fsz;
    if ((src = mmap(0, copysz, PROT_READ, MAP_SHARED, fdin, fsz)) == MAP_FAILED)
      err_sys("mmap error for input ");
    if ((dst = mmap(0, copysz, PROT_READ | PROT_WRITE, MAP_SHARED, fdout,
                    fsz)) == MAP_FAILED)
      err_sys("mmap error for output");

    memcpy(dst, src, copysz);
    munmap(src, copysz);
    munmap(dst, copysz);
    fsz += copysz;
  }
  exit(0);
}